Because of the consequences of a malfunction of a cable hoist or a winch, there is always a need for improvement in these devices. Various mechanisms have been used in the past to prevent a reverse rotation of a winch drum in use. However, it is believed that the brake systems in the prior art are subject to wear and deterioration from extended use and from aging of its components.
Examples of common brakes on winch drums are described in the following documents.
U.S. Pat. No. 2,181,359 issued on Nov. 28, 1939 to A. M. Barrett, discloses a hoist with a mechanism to slow down the descent of a load on the hoist cable. This braking mechanism is made of a friction brake pad mounted inside a brake drum.
U.S. Pat. No. 2,590,610 issued to G. S. Grosch on Mar. 25, 1952, discloses a braking mechanism for a winch including pawls coacting with a sun wheel mounted in a planetary gear system.
U.S. Pat. No. 2,649,281 issued to R. Hastings, Jr. on Aug. 18, 1953, discloses a winch including a pawl which engages the teeth of a stationary cylinder for braking the rotation of the drum in a reverse direction.
U.S. Pat. No. 3,109,525 issued to A. L. Welch on Nov. 5, 1963, discloses a winch including a brake band surrounding a ring gear to prevent the cable drum from rotating backwards.
U.S. Pat. No. 3,572,638 issued on Mar. 30, 1971 to M. T. Funabashi, discloses a winch and a brake. This braking mechanism comprises three pawls engaging with a ring gear. The pawls are operated by cams and springs to prevent reverse rotation of the winch drum. A pair of levers are used to disengage the pawls and to allow free rotation of the winch drum.
U.S. Pat. No. 4,328,954 issued to A. T. Logus on May 11, 1982, discloses another winch including a fail-safe disc-type friction brake.
U.S. Re 36,216 issued to T. M. Telford on Jun. 1, 1999, discloses a winch with an automated brake including cone-shaped brake shoes mounted on the driving shaft to cause a braking action to the drum.
Winches and hoists are often subjected to stresses beyond their safety ratings. Winches and hoists are used in all kind of weather conditions and can be stored away for long periods of time between uses. Therefore, in addition to failure in use from excessive strain, these equipments are susceptible of failure by aging of their components.
Although the winches and hoists of the prior art deserve undeniable merits, there is a need in this field for a winch brake that has few moving parts; that is not subject to wear or to aging, and that does not require periodic adjustment.